The present invention relates to a vertebral rod for a spinal osteosynthesis instrumentation, this rod having a constant diameter throughout its length and being adapted to receive bone anchorage implants. Complementarily, the invention also relates to a spinal osteosynthesis instrumentation comprising at least one of said rod and corresponding bone anchorage means fixed to the rod.
As is known, when an intervertebral disc is pinched, the adjacent vertebral bodies move toward each other and this causes a compression of the nerve roots and corresponding pain to the patient. It therefore becomes necessary to proceed to a surgical intervention to effect a correction, first by a distraction for separating the vertebral bodies and then by a compression for restoring the lumbar lordosis, i.e. the natural physiological curvature of the considered spinal segment.
In other cases, the vertebral column is deformed and asymmetric, which results in an abnormal curvature of the corresponding spinal segment. The surgical correction involves the use of implants fixed to the vertebrae and interconnected by a vertebral rod. In order to align the vertical column, a compression movement is necessary during which the implants slide along the rod and bring the vertebrae back to the desired orientation.
Subsequent to interventions of this type, the pain experienced by the subject is eliminated and the deformations are corrected. However, there remains a residual length of rod beyond the anchorage implants consituting a useless and even dangerous projecting part. Indeed, this end of the rod may alter the adjacent parts, in particular the articular elements located above and below, and damage the capsule of the upper articular elements.
This is the reason why some surgeons cut off this projecting end in situ. But such an operation requires large pliers for rods which may reach a diameter of 6 to 7 mm and cannot be effected without risk: indeed, the surgeon must exert a considerable force during which the pliers is liable to slip into the body of the patient and harm him, in particular after the inevitable jerk which occurs at the end of the cutting, and moreover the space taken up by the noses of the pliers is often excessive for the size of the spinal column.
Further, there is a definite risk of the ejection of the cut-off terminal member in the tissues, above all if the intervention occurs from the front. Indeed, the cut-off terminal member may drop into the peripheral muscles or behind the lungs or heart of the patient and become very difficult to remove. Lastly, the cut leaves an aggressive pointed end of the rod liable to harm the patient.